Chiral vibrations and collective bands in $^{104}$Mo

High spin states of the neutron-rich $^{104}$Mo nucleus which is known to be triaxial have been reinvestigated by analyzing the $\gamma$-rays in the spontaneous fission of $^{252}$Cf with Gammasphere. Both $\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$-$\gamma$ coincidence data were analyzed. A new $\Delta$I=1 band has been discovered. The new band is proposed to have a tentative 5$^-$ band head and form a class of chiral doublets with another 4$^-$ band previously found by our group [1]. Angular correlation measurements have been performed to determine spin and parity of the 4$^-$ chiral band head. The energies of the two sets of chiral bands are very similar to the chiral bands observed in $^{106}$Mo [2], e.g. the two 5$^-$ levels in $^{104}$Mo are at 2211.9 and 2276.8 keV with $\Delta$E=65 keV and in $^{106}$Mo, 1952.4 and 2090.6 keV with $\Delta$E=138 keV [2]. Now at every spin 5$^-$, 6$^-$, 7$^-$, 8$^-$, the separation energies of the same spin states are about a factor of two smaller than in $^{106}$Mo. This indicates even better agreement with expectations for two sets of chiral bands. [1] E.F. Jones et al., Physics of Atomic Nuclei, Vol. 69, 1198 (2006). [2] S.J. Zhu et al., Eur. Phys. J. A 25, 459 (2005).